This is what I found:
Another treatment proven to be successful is bone marrow transplant. Bone marrow from the horse’s sternum is extracted and then transplanted into the area of damage. Here again, the full mechanism of how this works is unknown, but it is believed that within the bone marrow are chemical and cell mediators that stimulate healing, including stem cells.
This leads us into another area of exciting treatment options: stem cell therapy. It is now possible to extract stem cells from a horse’s own fat, and then use those cells for healing. Stem cells are those that haven’t differentiated into any specific type ofcell yet: They still have the potential to become skin, bone, tendon, ligament, et cetera. It’s an exciting concept because it means these cells can be placed in damaged tissue, allowing the tissue to then regenerate.
Another therapy is IRAP (interleukin-1 receptor antagonist protein). IRAP is a chemical mediator in the blood that stops the bad chemical mediators in the blood produced by inflammation from being able to do damage, and allows the good chemical mediators to work more effectively. Blood from the horse is taken and incubated on special glass beads which grow the IRAP. The IRAP is then harvested and injected into the injury site. Unfortunately, this therapy is not widely available yet, but that may change."
Never heard of it before.